Brandon Sanderson
The second thing I tried writing was a short story set in the Mistborn world a few hundred years after The Hero of Ages. This one just didn’t work; the characters weren’t gripping for me. More importantly, it just didn’t FEEL like a Mistborn book. I got about one scene into it.
As I was working on it, however, I did some worldbuilding on this time period in Scadrial’s history. I got to thinking about what was wrong with the short story, and why it didn’t feel right. This grew into an outline regarding a completely different story—with no overlap of characters—set in the same time period. I nurtured this and started writing, and it felt right from the get-go. I had the right tone, so I kept writing, expanding my outline, letting the story grow as big as it wanted to be.
In the end, I had an 85,000-word novel that I named Mistborn: The Alloy of Law.